NASA's Navigation and Ancillary Information Facility (NAIF) offers NASA flight projects and NASA funded researchers the "SPICE" observation geometry information system to assist scientists in planning and interpreting scientific observations from space-based instruments aboard robotic planetary spacecraft. SPICE is also used in support of engineering tasks associated with these missions. While planetary missions were the original focus, today SPICE is also used on some heliophysics and earth science missions.
All aspects related to licensing of the software are provided here: https://naif.jpl.nasa.gov/naif/rules.html